Volatile organic compounds from second-hand smoke may increase susceptibility of children through oxidative stress damage

Although humans are generally exposed to second-hand smoke (SHS), volatile organic compounds (VOCs) exposure derived from SHS and its health hazard to non-smokers are rarely investigated. Thus, we examined the effects of SHS on VOCs exposure and oxidative stress damage via a passive smoking simulation experiment in 6 children and 7 adults. To further validate the studied urinary VOC metabolites as biomarkers for passive smoking, 259 children were recruited. The levels of 8-hydroxy-2'-deoxyguanosine (8-OHdG), malonaldehyde (MDA), trans-3'-hydroxycotinine (OH-Cot) and 31 VOC metabolites in urine were determined. The results showed that the geomean concentrations of 17 VOC metabolites in urine of children were 26.5%-138% higher than those of adults after passive smoking. The levels of urinary 8-OHdG, MDA and OH-Cot increased by 24.6%, 18.8% and 600% in children, but only 1.25%, 10.3% and 116% in adults, respectively. Therefore, children are more vulnerable to SHS than adults. After exposure to SHS, the levels of 8 urinary VOC metabolites of benzene, acrylonitrile, 1-bromopropane, propylene oxide, toluene, methyl methacrylate and cyanide increased by 60.9%-538% within 23 h. These 8 VOC metabolites were also significantly associated with 8-OHdG or MDA in urine (p < 0.01). Therefore, exposure to VOCs caused by SHS increases body oxidative stress damage. OH-Cot level higher than 2.00 mu g/g Cr can be used as a threshold of passive smoking. The levels of urinary s-benzylmercapturic acid (BMA) and s-phenylmercapturic acid (PMA) in children increased by 494% and 728% within 6 h after passive smoking, respectively. Population validation study indicated that BMA and PMA levels were significantly elevated in children exposed to SHS. Therefore, in addition to OH-Cot, urinary BMA and PMA are potentially useful short-term biomarkers of passive smoking. Future studies should focus on the differences in VOC metabolism and detoxification mechanisms between children and adults.